In a recoil operated self-loading firearm the “recoil” motion caused by firing is harnessed to unlock a portion that moves relative to the handgrip (in the case of a hand gun) or buttstock (in the case of a rifle). This relative motion is used to eject the spent cartridge case and to load another cartridge into the firing chamber, from a stock of cartridges held in a magazine.
The unlocking of the two portions, however, cannot take place too quickly after firing the cartridge, because immediately after firing the barrel contains highly pressurized gas that would be dangerous if released prematurely. Too overcome this problem many mechanisms have been invented for unlocking the two firearm sections, after a short delay, to permit the bullet to leave the barrel and the barrel to depressurize.
Unfortunately, the mechanisms currently employed to use the recoil of the firearm in locked breech pistols all suffer from one or both of two drawbacks. First, for currently available mechanisms, the delay is inversely proportional to the intensity of the ordinance used. Accordingly, the need for a sufficient unlocking delay places an upper limit on ordinance intensity. Second, many unlocking mechanisms rely on a limited movement of the barrel of the firearm. Any structure in which the barrel of the firearm is not fixed to the part that is held by the operator has the potential for degrading shooting accuracy.
Also currently available, and employed particularly in self-loading rifles, is a mechanism by which the pressurized gas present in the gun barrel directly after a shot is fired is employed to eject the spent cartridge case and load an unfired cartridge into the firing chamber. Unfortunately, the complexity of this type of mechanism adds to the weight of the firearm and may be subject to jamming due to incompletely burned propellant powder granules that may be present in the system immediately after shooting. Although it appears that one handgun has been designed utilizing this scheme, it is so heavy as to have limited utility.